大豆重迎茬减产的原因及农艺对策研究Ⅳ.重迎茬大豆的土壤养分与养分吸收

连续8年在黑龙江省5个生态区9个9区固定轮作场圃综合试验，试验区专项研究，框区、盆栽试验，实验室分析，以及大量的大面积生产调查，发现大豆重迎茬种植，根际土壤养分虽然在理论计算时，会出现氮素营养亏缺，但是生产实际中，由于施肥的缘故，大豆重迎茬并没有造成养分的明显偏耗，不仅氮磷钾三元素如此，硼、钼、锰、锌等微量元素也是不同轮作方式间没有明显的差异；在不施肥的盆栽条件下，大豆以及玉米、小麦重茬种植都比正茬轮作多消耗了土壤中的主要营养元素，其中重茬大豆对全磷和速效钾的消耗高于重茬玉米、重茬小麦；大豆重迎茬种植，植株对营养的吸收能力发生了变化，对于大多数营养元素、特别是对于氮磷钾三要素的吸收能力下降，但是，对于钙、镁、铁等微量元素的吸收量增加；增施钾肥能显著地提高重迎茬大豆的产量。这一切都说明根际土壤养分的变化以及根对养分吸收能力减弱对重迎茬大豆的生长发育和产量有一定的影响，但并不是大豆重迎茬减产的主要原因。

STUDY ON THE REASONS OF REDUCING GRAIN YIELD IN SOYBEAN PLANTED CONTINUOUSLY AND THE WAYS TO GET MORE OUTPUT Ⅳ.Soil Natrition and Absorbabiluty in Continuous and Every Other One Year Copping Soybean

The experiments on continuous and every other one year cropping soybean in 5 ecological regions of Heilongjiang Province had been carried out for 8 years since 1993. In the same time, the investigation was made in soybean fields. The result showed that: according to theoretics, soil of nutrition in continuous and every other one year cropping soybean would be expended unilaterally. But, in the practice of production, there was not unilateral expending significantly when soybeans were planted continuously and alternatively. It was not only for N, P and K, but also for B, Mo, Mn, Zn, etc. The amount of element and microelement took from soil was not significant different among rotation patterns. In potting expariment without fertilizer, mare main nutritional elements were expended in continuos cropping soybean maize and wheat than that in normal rotation Among them, the amount of whole phosphorus and quick acting potassium, expended in continuous-alternate soybeans, was more than that in continuous-alternate corn and wheat. The ability to absorb nutrition was changed, when soybeans were planted continuously and alternately. The ability to absorb most elements, especially, to absorb nitrogen, phosphorus and potassium was reduced. But the ability to absorb calcium, magnesium, iron etc nas increesed. To apply potassium could increase the output of soybeans in continuous and every ther one year cropping soynean. All of those abovementioned showed it was an important reason to reduce output of continuous-alternate soybeans the amount of soil nutrition around roots was changed and the absorbability of nutrition was reduced.